This invention relates to an air pollution control fuel tank cap which also aids in the recovery of fuel vapors from a fuel tank and the subsequent economical consumption of those vapors in the fuel system of an internal combustion engine, furnace, or the like.
It is well known that vapors evolved from the fuel tanks of automobiles, oil furnaces, and the like contribute to air pollution. This is due in part to the fact that it has been customary to vent the fuel tank to the atmosphere, thus permitting the evaporative emission of hydrocarbon vapor into the atmosphere. This situation is aggravated by fuel tank running losses caused by the flow of heated air past the tank and the tank diurnal cycle or the daily variation in temperature which causes tank breathing and the resultant loss of vapor, even if the fuel in the tank is at rest. Accordingly, not only does the emission of hydrocarbon vapors from a fuel tank contribute to air pollution, but the loss of such vapors to the atmosphere is extremely uneconomical in wasting fuel.